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LM3478: Load transient

na na78
Guru 16770 points

Part Number: LM3478
Other Parts Discussed in Thread: TPS43061, LM5170

Hi

We want to compare the performance of load transient between LM3478 and TPS43061.

The datasheet of TPS43061 offers the following load transient figure but LM3478 is not.

Do you have similar data for LM3478?

Which device is better for load transient response?

Requirement:

Input : 6V to 8.4V

Output: 19V/1A

Efficiency : 90% target

Load transient : 2% - 3% target

BestRegards

  • 0
    TI__Guru* 79375 points
    We don't have the results for apple to apple comparison. The step load response is the results of loop compensation, and the LM3478 can be made to perform similarly. The major difference is, the TPS43061 uses synchronous rectifier, means its efficiency will be higher than using LM3478. Since the TPS43061 is synchronous boost, its step load response overshoot and undershoot as well as the recovery time are symmetrical. However, the LM3478 may show slower recovery from overshoot when the step load jumps into deep discontinuous conduction.
  • 0 in reply to Youhao Xi
    Guru 16770 points
    Hi Youhao

    Thank you for your reply.

    >LM3478 may show slower recovery from overshoot when the step load jumps into deep discontinuous conduction.

    Could you show us some example figure if you can share?
    It is OK if it is not LM3478.
    We want to refer the example that asynchronous rectification may show the slower recovery to the overshoot as load response.

    BestRegards
  • 0 in reply to na na78
    TI__Guru* 79375 points

    See below from a different circuit showing unbalanced step load response:  load 0A to 10A.  Vout can stay longer before recovery.

  • 0 in reply to Youhao Xi
    Guru 16770 points
    Hi Youhao

    Thank you for your reply.

    Is it possible for us to know what the device is?

    BestRegards
  • 0 in reply to na na78
    TI__Guru* 79375 points
    This was captured on a LM5170 circuit which will run in dcm at light load. The response is typical for all dcm circuit: Vout overshoot decays slowly after load step change to light or no load.
  • 0 in reply to Youhao Xi
    Guru 16770 points
    Hi Youhao

    Thank you!

    BestRegards